The present invention relates to conductivity sensors and to method for using conductivity sensors for sensing the conductivity of a fluid. Conductivity sensors are used to measure the conductivity of fluids for numerous types of apparatus. For example, conductivity sensors are used to measure the conductivity of fluids that flow through heat exchangers that control the temperature of equipment, such as semiconductor processing equipment. There are currently more than 15,000 heat exchanger systems in production semiconductor processing equipment that use conductivity sensors to measure the conductivity of cooling fluid flowing through heat exchangers.